The present invention relates to an electronic fuel injection control system for internal combustion engines, and more particularly to a calculation unit for use in the control system for determining an optimum fuel injection time in relation to the quantity of air drawn into the engine.
In one example of such a conventional fuel injection control system as disclosed in the U.S. Pat. No. 3,750,631 issued on Aug. 7, 1973, the position of a static plate used to measure the amount of air sucked through the intake manifold controls the wiper of a potentiometer that is connected to control either the rate of charging or of discharging of a single capacitor that is charged in synchronism with the rotation of the engine crankshaft. The length of time that the capacitor takes to discharge determines the length of time that the fuel injection valve is open. Although such a fuel injection control system is suitable for determining the fuel injection time in synchronism with the rotational period of the engine, it is disabled to vary the timing for determination of the fuel injection time in response to operating conditions of the engine or to independently determine the fuel injection time for each cylinder of the engine.